Association of urinary KIM-1, L-FABP, NAG and NGAL with incident end-stage renal disease and mortality in American Indians with type 2 diabetes mellitus

Urine biomarkers in type 2 diabetes mellitus with or without microvascular complications

OBJECTIVE

To investigate the distribution of nine (9) urine biomarkers in people living with type 2 diabetes mellitus (T2DM), with or without microvascular complications.

METHODS

In total, 407 people with T2DM were enrolled from 2021 to 2022. According to diabetic retinopathy (DR) and urinary albumin-creatinine ratio (UACR), the 407 people were divided into four (4) groups, DR(-)UACR(-), DR(+)UACR(-), DR(-)UACR(+), and DR( + )UACR(+). In addition, 112 healthy volunteers were enrolled during the same period. The nine (9) urine markers included α1-microglobulin (u-α1MG), immunoglobulin G (u-IgG), neutrophil gelatinase-associated lipid carrier protein (u-NGAL), cystatin C (u-CysC), retinol-binding protein (u-RBP), β2-microglobulin (u-β2MG), N-acetyl-β-D-glucosaminidase (u-NAG), transferrin (u-Trf), and collagen type IV (u-Col). For each marker, the respective level of 97.5 percentile in healthy volunteers was taken as an upper reference limit.

RESULTS

Among the 407 people, 248 individuals (61%) were DR(-)UACR(-), 100 (25%) were DR(-)UACR(+), 37 (9%) were DR(+)UACR(-), and 22 (5%) were DR(+)UACR(+). The u-NAG/Cr biomarker level showed a significant difference between healthy participants and people with T2DM. In the DR(-)UACR(-)group, u-Trf/Cr showed the highest positive rate (21.37%), followed by u-IgG/Cr (14.52%); u-NAG/Cr (10.48%); u-β2MG/Cr (4.44%); u-CysC/Cr (4.03%); u-NGAL/Cr (4.03%); u-RBP/Cr (2.82%); u-α1MG/Cr (2.42%); 17.34% of people with T2DM showed multiple biomarkers positive (≥2 biomarkers). The positive rates of one biomarker (21.33%) and two biomarkers (18.67%) in people who have less than five (5) years of T2DM were almost close to those of the DR(-)UACR(-) group (21.37%, and 12.10%, respectively).

CONCLUSION

Renal tubule biomarkers may be used as an indicator in the early detection and monitoring of renal injury in diabetes mellitus. The u-NAG biomarker should be measured for the people with T2DM of the first-time diagnosis.

Urinary non-albumin protein-creatinine ratio is an independent predictor of mortality in patients with type 2 diabetes: a retrospective cohort study

Albuminuria is a well-known predictor of chronic kidney disease in patients with type 2 diabetes mellitus (DM). However, proteinuria is associated with chronic complications in patients without albuminuria. In this retrospective cohort study, we explored whether non-albumin proteinuria is associated with all-cause mortality and compared the effects of non-albumin proteinuria on all-cause mortality between patients with and without albuminuria. We retrospectively collected data from patients with type 2 DM for whom we had obtained measurements of both urinary albumin-to-creatinine ratio (UACR) and urinary protein-to-creatinine ratio (UPCR) from the same spot urine specimen. Urinary non-albumin protein-creatinine ratio (UNAPCR) was defined as UPCR-UACR. Of the 1809 enrolled subjects, 695 (38.4%) patients died over a median follow-up of 6.4 years. The cohort was separated into four subgroups according to UACR (30 mg/g) and UNAPCR (120 mg/g) to examine whether these indices are associated with all-cause mortality. Compared with the low UACR and low UNAPCR subgroup as the reference group, multivariable Cox regression analyses indicated no significant difference in mortality in the high UACR and low UNAPCR subgroup (hazard ratio [HR] 1.189, 95% confidence interval [CI] 0.889-1.589, P = 0.243), but mortality risks were significantly higher in the low UACR and high UNAPCR subgroup (HR 2.204, 95% CI 1.448-3.356, P < 0.001) and in the high UACR with high UNAPCR subgroup (HR 1.796, 95% CI 1.451-2.221, P < 0.001). In the multivariable Cox regression model with inclusion of both UACR and UNAPCR, UNAPCR ≥ 120 mg/g was significantly associated with an increased mortality risk (HR 1.655, 95% CI 1.324-2.070, P < 0.001), but UACR ≥ 30 mg/g was not significantly associated with mortality risk (HR 1.046, 95% CI 0.820-1.334, P = 0.717). In conclusion, UNAPCR is an independent predictor of all-cause mortality in patients with type 2 DM.

Evaluation of N-acetyl-β-D-glucosaminidase as a prognostic marker for diabetic nephropathy in type 2 diabetics: systematic review and meta-analysis

OBJECTIVE

This review aimed to assess the utility of urinary N-acetyl-β-D-glucosaminidase (uNAG) as a prognostic biomarker for nephropathy in patients with type 2 diabetes mellitus.

METHODS

The search for relevant studies was conducted across multiple databases, including PubMed (Medline), EMBASE, LILACS, CENTRAL, IBECS, and gray literature. We employed a random effects model to calculate the standardized mean difference and 95% confidence interval. Furthermore, we assessed heterogeneity using Cochrane's Q test and Higgins' I2 statistics.

RESULTS

This review included a total of 16 articles involving 1669 patients, with 13 being case-control studies and three being cohorts. The meta-analysis conducted across all studies revealed significant heterogeneity. However, subgroup analysis of four studies indicated that an increase in uNAG among normoalbuminuric patients was associated with the development of macroalbuminuria (DMP = - 1.47; 95% CI = - 1.98 to 0.95; p < 0.00001; I2 = 45%). Conversely, it did not demonstrate effectiveness in predicting the development of microalbuminuria (DMP = 0.26; 95% CI = - 0.08 to 0.60; p = 0.13; I2 = 17%).

CONCLUSIONS

Elevated uNAG levels in normoalbuminuric patients may indicate an increased risk for the development of macroalbuminuria, but not microalbuminuria. However, the high heterogeneity observed among the studies highlights the necessity for further research to validate these findings.

Astragaloside IV attenuates renal tubule injury in DKD rats via suppression of CD36-mediated NLRP3 inflammasome activation

Background

In recent years, diabetic kidney disease (DKD) has emerged as a prominent factor contributing to end-stage renal disease. Tubulointerstitial inflammation and lipid accumulation have been identified as key factors in the development of DKD. Earlier research indicated that Astragaloside IV (AS-IV) reduces inflammation and oxidative stress, controls lipid accumulation, and provides protection to the kidneys. Nevertheless, the mechanisms responsible for its protective effects against DKD have not yet been completely elucidated.

Purpose

The primary objective of this research was to examine the protective properties of AS-IV against DKD and investigate the underlying mechanism, which involves CD36, reactive oxygen species (ROS), NLR family pyrin domain containing 3 (NLRP3), and interleukin-1β (IL-1β).

Methods

The DKD rat model was created by administering streptozotocin along with a high-fat diet. Subsequently, the DKD rats and palmitic acid (PA)-induced HK-2 cells were treated with AS-IV. Atorvastatin was used as the positive control. To assess the therapeutic effects of AS-IV on DKD, various tests including blood sugar levels, the lipid profile, renal function, and histopathological examinations were conducted. The levels of CD36, ROS, NLRP3, Caspase-1, and IL-1β were detected using western blot analysis, PCR, and flow cytometry. Furthermore, adenovirus-mediated CD36 overexpression was applied to explore the underlying mechanisms through in vitro experiments.

Results

In vivo experiments demonstrated that AS-IV significantly reduced hyperglycemia, dyslipidemia, urinary albumin excretion, and serum creatinine levels in DKD rats. Additionally, it improved renal structural abnormalities and suppressed the expression of CD36, NLRP3, IL-1β, TNF-α, and MCP-1. In vitro experiments showed that AS-IV decreased CD36 expression, lipid accumulation, and lipid ROS production while inhibiting NLRP3 activation and IL-1β secretion in PA-induced HK-2 cells.

Conclusion

AS-IV alleviated renal tubule interstitial inflammation and tubule epithelial cell apoptosis in DKD rats by inhibiting CD36-mediated lipid accumulation and NLRP3 inflammasome activation.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) as a potential early biomarker for diabetic nephropathy: a meta-analysis

BACKGROUND

Diabetic nephropathy (DN) is a prevalent and chronic, severe complication of diabetes, representing a serious global health concern. Early detection of DN is essential for initiating timely and effective therapeutic interventions and accurately assessing prognosis. Neutrophil Gelatinase-Associated Lipocalin (NGAL), a low molecular weight protein, has emerged as a potential biomarker for DN due to its association with renal injury and its ability to provide early indications of kidney damage. NGAL levels in both serum and urine are elevated in individuals with renal damage, making it a valuable biomarker for detecting early signs of kidney impairment in the context of diabetes. This study aims to investigate the utility of NGAL as an early biomarker for DN and explore its correlation with various clinical parameters associated with the disease. Understanding the relationship between NGAL levels and clinical parameters such as glycemic control, renal function, blood pressure, and duration of diabetes is crucial for comprehensively evaluating the potential of NGAL as a diagnostic and prognostic tool for DN. Furthermore, assessing the sensitivity and specificity of NGAL in detecting early-stage DN will provide valuable insights into its clinical applicability and reliability.

METHODOLOGY

A planned meta-analysis was conducted following PRISMA and MOOSE guidelines. The PubMed database was searched from January 2016 to June 2023 for English-language studies on DN and NGAL. Fifteen eligible studies were included as per the criteria. Data on serum NGAL levels in DN patients and healthy controls were analyzed using Stata 16.0 software.

RESULT

The study revealed a significantly higher mean serum NGAL level in DN patients (168.08 ng/ml, 95% CI: 105.50-230.67) compared to healthy controls (75.02 ng/ml, 95% CI: 43.02-107.03), demonstrating NGAL's potential as a biomarker (P=0.01).

CONCLUSION

NGAL offers a powerful tool for DN diagnosis, staging, and monitoring, surpassing traditional markers in sensitivity. Challenges include defining universal threshold values and ensuring consistent test performance across diverse clinical settings. The study underscores NGAL's potential in transforming DN diagnosis and management.

Renogrit attenuates Vancomycin-induced nephrotoxicity in human renal spheroids and in Sprague-Dawley rats by regulating kidney injury biomarkers and creatinine/urea clearance

Vancomycin, is widely used against methicillin-resistant bacterial infections. However, Vancomycin accumulation causes nephrotoxicity which leads to an impairment in the filtration mechanisms of kidney. Traditional herbal medicines hold potential for treatment of drug-induced nephrotoxicity. Herein, we investigated protective properties of plant-based medicine Renogrit against Vancomycin-induced kidney injury. Phytometabolite analysis of Renogrit was performed by UHPLC. Spheroids formed from human proximal tubular cell (HK-2) were used for in vitro evaluation of Vancomycin-induced alterations in cell viability, P-gp functionality, NAG, KIM-1 levels, and mRNA expression of NGAL and MMP-7. The in vivo efficacy of Renogrit against Vancomycin-induced nephrotoxicity was further evaluated in Sprague-Dawley (SD) rats by measurement of BUN, serum creatinine, and their respective clearances. Moreover, eGFR, kidney-to-body weight ratio, GSH/GSSG ratio, KIM-1, NAG levels and mRNA expression of KIM-1 and osteopontin were also analyzed. Changes in histopathology of kidney and hematological parameters were also observed. Renogrit treatment led to an increase in cell viability, normalization of P-gp functionality, decrease in levels of NAG, KIM-1, and reduction in mRNA expression of NGAL and MMP-7. In Vancomycin-challenged SD rats, Renogrit treatment normalized altered kidney functions, histological, and hematological parameters. Our findings revealed that Renogrit holds a clinico-therapeutic potential for alleviating Vancomycin-associated nephrotoxicity.

Urinary Liver-Type Fatty Acid Binding Protein, a Biomarker for Disease Progression, Dialysis and Overall Mortality in Chronic Kidney Disease

Chronic kidney disease (CKD) is a major public health concern with an increasing proportion of sufferers progressing to renal replacement therapy (RRT). Early identification of those at risk of disease progression could be key in improving outcomes. We hypothesise that urinary liver-type fatty acid binding protein (uL-FABP) may be a suitable biomarker for CKD progression and can add value to currently established biomarkers such as the urinary protein-to-creatinine ratio (uPCR). A total of 583 participants with CKD 1-5 (not receiving renal replacement therapy) entered a 2 yr prospective longitudinal study. UPCR and uL-FABP were measured at baseline and CKD progression was defined as either (i) a decline in eGFR of >5 mL/min/1.73 m2 or an increase in serum creatinine by 10% at 1 yr; (ii) a decline in eGFR of >6 mL/min/1.73 m2 or an increase in serum creatinine by 20% at 2 yrs; or (iii) the initiation of RRT. A combined outcome of initiating RRT or death was also included. Approximately 40% of participants showed CKD progression. uL-FABP predicted CKD progression at both years 1 and 2 (OR 1.01, p < 0.01). Sensitivity and specificity were comparable to those of uPCR (AUC 0.623 v 0.706) and heat map analysis suggested that uL-FABP in the absence of significant proteinuria can predict an increase in serum creatinine of 10% at 1 yr and 20% at 2 yrs. The risk of the combined outcome of initiating RRT or death was 23% higher in those with high uL-FABP (p < 0.01) independent of uPCR. uL-FABP appears to be a highly sensitive and specific biomarker of CKD progression. The use of this biomarker could enhance the risk stratification of CKD and its progression and should be assessed further.

Revisiting the Role of NAG across the Continuum of Kidney Disease

Acute and chronic kidney diseases are an evolving continuum for which reliable biomarkers of early disease are lacking. The potential use of glycosidases, enzymes involved in carbohydrate metabolism, in kidney disease detection has been under investigation since the 1960s. N-acetyl-beta-D-glucosaminidase (NAG) is a glycosidase commonly found in proximal tubule epithelial cells (PTECs). Due to its large molecular weight, plasma-soluble NAG cannot pass the glomerular filtration barrier; thus, increased urinary concentration of NAG (uNAG) may suggest injury to the proximal tubule. As the PTECs are the workhorses of the kidney that perform much of the filtration and reabsorption, they are a common starting point in acute and chronic kidney disease. NAG has previously been researched, and it is widely used as a valuable biomarker in both acute and chronic kidney disease, as well as in patients suffering from diabetes mellitus, heart failure, and other chronic diseases leading to kidney failure. Here, we present an overview of the research pertaining to uNAG’s biomarker potential across the spectrum of kidney disease, with an additional emphasis on environmental nephrotoxic substance exposure. In spite of a large body of evidence strongly suggesting connections between uNAG levels and multiple kidney pathologies, focused clinical validation tests and knowledge on underlining molecular mechanisms are largely lacking.

Novel biomarkers for diabetic kidney disease

Although diabetic kidney disease (DKD) remains one of the leading causes of reduced lifespan in patients with diabetes mellitus; its prevalence has failed to decline over the past 30 years. To identify those at high risk of developing DKD and disease progression at an early stage, extensive research has been ongoing in the search for prognostic and surrogate endpoint biomarkers for DKD. Although biomarkers are not used routinely in clinical practice or prospective clinical trials, many biomarkers have been developed to improve the early identification and prognostication of patients with DKD. Novel biomarkers that capture one specific mechanism of the DKD disease process have been developed, and studies have evaluated the prognostic value of assay-based biomarkers either in small sets or in combinations involving multiple biomarkers. More recently, several studies have assessed the prognostic value of omics- based biomarkers that include proteomics, metabolomics, and transcriptomics. This review will first describe the biomarkers used in current practice and their limitations, and then summarize the current status of novel biomarkers for DKD with respect to assay- based protein biomarkers, proteomics, metabolomics, and transcriptomics.

Performance of urinary liver-type fatty acid-binding protein in diabetic nephropathy: A meta-analysis

Aims

Diabetic nephropathy (DN) is one of the main causes of chronic kidney disease (CKD), which increases the risk of cardiovascular diseases and progresses to end-stage renal failure. Thus, early diagnostic markers for diabetic patients are urgently needed to improve the prognosis of DN and predict DN progression.

Materials and methods

PubMed, MEDLINE, EMBASE, and Scopus were searched for publications until February 24, 2021. Review Manager 5.4 software was used for meta-analysis. We performed the heterogeneity test using the I² statistic: P < 0.1 and I²> 50% meant statistical significance.

Results

We included 13 studies. The urinary liver-type fatty acid-binding protein (uL-FABP) concentrations in the normal albuminuria group were significantly higher than those in the normal control group without diabetes mellitus (DM) [P = 0.009, SMD 1.72, 95% CI (0.44, 2.99)]. Urinary F-LABP levels were elevated in the macroalbuminuria group compared with those in the microalbuminuria group with DM [P = 0.002, SMD 2.82, 95% CI (1.03, 4.61)]. Urinary L-FABP levels were also significantly increased in the progression and CKD groups compared with non-progression and CKD subjects with DM [P = 0.02, P < 0.00001, respectively]. Furthermore, uL-FABP concentrations were positively correlated with the albumin-to-creatinine ratio and systolic blood pressure in patients with DM [Summary Fisher’s Z = 0.58 P < 0.00001; Summary Fisher’s Z = 0.24 P < 0.0001, respectively] and negatively correlated with estimated glomerular filtration rate in patients with DM [Summary Fisher’s Z = −0.36, P < 0.0001].

Conclusion

Urinary L-FABP may be a potential marker for the detection of all stages of DN and for the prediction of the progression and severity of DN in patients with type 1 and 2 DM.

Review of potential biomarkers of inflammation and kidney injury in diabetic kidney disease

Diabetic kidney disease is expected to increase rapidly over the coming decades with rising prevalence of diabetes worldwide. Current measures of kidney function based on albuminuria and estimated glomerular filtration rate do not accurately stratify and predict individuals at risk of declining kidney function in diabetes. As a result, recent attention has turned towards identifying and assessing the utility of biomarkers in diabetic kidney disease. This review explores the current literature on biomarkers of inflammation and kidney injury focussing on studies of single or multiple biomarkers between January 2014 and February 2020. Multiple serum and urine biomarkers of inflammation and kidney injury have demonstrated significant association with the development and progression of diabetic kidney disease. Of the inflammatory biomarkers, tumour necrosis factor receptor-1 and -2 were frequently studied and appear to hold most promise as markers of diabetic kidney disease. With regards to kidney injury biomarkers, studies have largely targeted markers of tubular injury of which kidney injury molecule-1, beta-2-microglobulin and neutrophil gelatinase-associated lipocalin emerged as potential candidates. Finally, the use of a small panel of selective biomarkers appears to perform just as well as a panel of multiple biomarkers for predicting kidney function decline.

Diagnosis of Cardiac Surgery-Associated Acute Kidney Injury: State of the Art and Perspectives

Diagnosis of cardiac surgery-associated acute kidney injury (CSA-AKI), a syndrome of sudden renal dysfunction occurring in the immediate post-operative period, is still sub-optimal. Standard CSA-AKI diagnosis is performed according to the international criteria for AKI diagnosis, afflicted with insufficient sensitivity, specificity, and prognostic capacity. In this article, we describe the limitations of current diagnostic procedures and of the so-called injury biomarkers and analyze new strategies under development for a conceptually enhanced diagnosis of CSA-AKI. Specifically, early pathophysiological diagnosis and patient stratification based on the underlying mechanisms of disease are presented as ongoing developments. This new approach should be underpinned by process-specific biomarkers including, but not limited to, glomerular filtration rate (GFR) to other functions of renal excretion causing GFR-independent hydro-electrolytic and acid-based disorders. In addition, biomarker-based strategies for the assessment of AKI evolution and prognosis are also discussed. Finally, special focus is devoted to the novel concept of pre-emptive diagnosis of acquired risk of AKI, a premorbid condition of renal frailty providing interesting prophylactic opportunities to prevent disease through diagnosis-guided personalized patient handling. Indeed, a new strategy of risk assessment complementing the traditional scores based on the computing of risk factors is advanced. The new strategy pinpoints the assessment of the status of the primary mechanisms of renal function regulation on which the impact of risk factors converges, namely renal hemodynamics and tubular competence, to generate a composite and personalized estimation of individual risk.

Molecular Mechanisms of Diabetic Kidney Disease

The inflammatory component of diabetic kidney disease has become of great interest in recent years, with genetic and epigenetic variants playing a fundamental role in the initiation and progression of the disease. Cells of the innate immune system play a major role in the pathogenesis of diabetic kidney disease, with a lesser contribution from the adaptive immune cells. Other components such as the complement system also play a role, as well as specific cytokines and chemokines. The inflammatory component of diabetic kidney disease is of great interest and is an active research field, with the hope to find potential innovative therapeutic targets.

Usefulness of urinary tubule injury markers for predicting progression of renal dysfunction in patients with type 2 diabetes and albuminuria: The Fukuoka Diabetes Registry

AIMS

We prospectively investigated the association of urinary tubule injury markers with estimated glomerular filtration rate (eGFR) decline in Japanese patients with type 2 diabetes.

METHODS

Urinary kidney injury molecule 1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty-acid-binding protein (L-FABP), and urinary albumin-to creatinine ratio (UACR) were measured in 2,685 participants with type 2 diabetes. Renal outcomes were ≥ 30% decline in eGFR from the baseline and annual eGFR decline for 5 years.

RESULTS

In normoalbuminuric participants, no tubular markers were associated with ≥ 30% decline in eGFR or annual eGFR changes. In those with UACR ≥ 30 mg/gCr, hazard ratios for ≥ 30% eGFR decline were 1.37 (95% confident interval (CI) 1.07-1.75) for urinary KIM-1 (>1.5 µg/gCr), 1.46 (95% CI 1.13-1.66) for urinary NGAL (>16.4 µg/gCr), and 1.26 (95% CI 0.94-1.66) for urinary L-FABP (>12.5 µg/gCr), 2.61 (95% CI 1.64-4.17) for the combination of 3 tubular markers above the cutoff after multivariable adjustments including UACR and eGFR.

CONCLUSIONS

The current study demonstrated that urinary tubule injury markers and their combination were significant predictors for the future eGFR decline in those with type 2 diabetes and albuminuria independently of UACR and eGFR. Urinary tubular markers may be useful to identify high-risk patients with albuminuria.

Plasma Kidney Injury Molecule 1 in CKD: Findings From the Boston Kidney Biopsy Cohort and CRIC Studies

RATIONALE & OBJECTIVE

Plasma kidney injury molecule 1 (KIM-1) is a sensitive marker of proximal tubule injury, but its association with risks of adverse clinical outcomes across a spectrum of kidney diseases is unknown.

STUDY DESIGN

Prospective, observational cohort study.

SETTING & PARTICIPANTS

524 individuals enrolled into the Boston Kidney Biopsy Cohort (BKBC) Study undergoing clinically indicated native kidney biopsy with biopsy specimens adjudicated for semiquantitative scores of histopathology by 2 kidney pathologists and 3,800 individuals with common forms of chronic kidney disease (CKD) enrolled into the Chronic Renal Insufficiency Cohort (CRIC) Study.

EXPOSURE

Histopathologic lesions and clinicopathologic diagnosis in cross-sectional analyses, baseline plasma KIM-1 levels in prospective analyses.

OUTCOMES

Baseline plasma KIM-1 levels in cross-sectional analyses, kidney failure (defined as initiation of kidney replacement therapy) and death in prospective analyses.

ANALYTICAL APPROACH

Multivariable-adjusted linear regression models tested associations of plasma KIM-1 levels with histopathologic lesions and clinicopathologic diagnoses. Cox proportional hazards models tested associations of plasma KIM-1 levels with future kidney failure and death.

RESULTS

In the BKBC Study, higher plasma KIM-1 levels were associated with more severe acute tubular injury, tubulointerstitial inflammation, and more severe mesangial expansion after multivariable adjustment. Participants with diabetic nephropathy, glomerulopathies, and tubulointerstitial disease had significantly higher plasma KIM-1 levels after multivariable adjustment. In the BKBC Study, CKD in 124 participants progressed to kidney failure and 85 participants died during a median follow-up time of 5 years. In the CRIC Study, CKD in 1,153 participants progressed to kidney failure and 1,356 participants died during a median follow-up time of 11.5 years. In both cohorts, each doubling of plasma KIM-1 level was associated with an increased risk of kidney failure after multivariable adjustment (hazard ratios of 1.19 [95% CI, 1.03-1.38] and 1.10 [95% CI, 1.06-1.15] for BKBC and CRIC, respectively). There was no statistically significant association of plasma KIM-1 levels with death in either cohort.

LIMITATIONS

Generalizability and unmeasured confounding.

CONCLUSIONS

Plasma KIM-1 is associated with underlying tubulointerstitial and mesangial lesions and progression to kidney failure in 2 cohort studies of individuals with kidney diseases.

Epigenetic restoration of endogenous Klotho expression alleviates acute kidney injury-diabetes comorbidity

AIMS

The present study aimed at exploring the mechanisms behind Klotho regulation in hyperglycemia augmented AKI. In addition, epigenetic ways to restore the Klotho expression in AKI-diabetes comorbidity have been evaluated.

MAIN METHODS

Bilateral ischemia-reperfusion injury (IRI) and chemical hypoxia-reperfusion injury (HRI) were developed in diabetic rats and, NRK52E cells under high glucose conditions respectively, to mimic the AKI condition. Plasma, urine, tubular lysate of the kidney and NRK52E cell lysate were used for biochemical, ELISA, histology, immunoblotting, RT-PCR and RNA interference studies.

KEY FINDINGS

Hyperglycemia significantly aggravated IRI/HRI induced AKI as evidenced by biochemical and histological results. We also observed a significant increase in expressions of kidney specific histone deacetylases (HDACs), apoptotic and inflammatory proteins, and decrease in levels of endogenous Klotho, H3K9Ac and H3K27Ac proteins in hyperglycemic IRI/HRI groups.

SIGNIFICANCE

Diabetes comorbidity exaggerates AKI, where endogenous Klotho loss could be a potential connecting link. However, kidney-specific HDACs inhibition showed reno-protection via restoring the endogenous Klotho loss and thus prevention of inflammation and apoptosis, which could prove to be a potential therapeutic strategy against diabetes-AKI comorbidity.

Blood and Urine Biomarkers Predicting Worsening Kidney Function in Patients with Type 2 Diabetes Post-Acute Coronary Syndrome: An Analysis from the EXAMINE Trial

INTRODUCTION

Worsening kidney function (WKF) is frequent among patients with type 2 diabetes (T2D) and a recent acute coronary syndrome (ACS) and is associated with a poor prognosis. An accurate prediction of WKF is clinically important.

AIMS

Using data from the Cardiovascular Outcomes Study of Alogliptin in Patients with Type 2 Diabetes and Acute Coronary Syndrome trial including patients with T2D and a recent ACS, and a large biomarker panel incorporating proteins measured both in blood and urine, we aim to determine those with best performance for WKF prediction.

METHODS

WKF was defined as a ≥40% estimated glomerular filtration rate (eGFR) drop from baseline, eGFR <15 mL/min, or dialysis. Mixed-effects and time-updated Cox models were used.

RESULTS

5,131 patients were included from whom 222 (4.3%) developed at least one WKF episode over a median follow-up of 18 months. Patients who developed WKF were more frequently women, had longer diabetes duration, a more frequent heart failure history, higher anemia prevalence, and impaired kidney function. In multivariable models including all variables (clinical and biomarkers) independently associated with WKF with a p value ≤0.0001, blood kidney injury molecule 1 (KIM-1) was (by far) the variable with strongest WKF association, followed by anemia. KIM-1 alone provided good discrimination for WKF prediction (area under the curve = 0.73). Patients in the high KIM-1-derived risk tertile had a 6.7-fold higher risk of any WKF than patients classified as low risk. In time-updated Cox models, the occurrence of WKF was independently associated with a higher risk of death: adjusted hazard ratio = 4.93 (3.06-7.96), p value <0.0001.

CONCLUSION

Blood KIM-1 was the biomarker with the strongest association with WKF. The occurrence of WKF was independently associated with a higher risk of subsequent cardiovascular events and mortality.

High concentrations of triglycerides are associated with diabetic kidney disease in new-onset type 2 diabetes in China: Findings from the China Cardiometabolic Disease and Cancer Cohort (4C) Study

AIMS

The aims of this study were to evaluate the associations of metabolic abnormalities with incident diabetic kidney disease (DKD) and to explore whether dyslipidaemia, particularly high fasting triglyceride (TG), was associated with the development of DKD.

METHODS

In total, 11 142 patients with new-onset type 2 diabetes with baseline estimated glomerular filtration rates (eGFR) ≥60 mL/min/1.73 m² were followed up during 2011-2016. Incident DKD was defined as eGFR <60 mL/min/1.73 m² at follow-up. Multiple logistic regression analysis was conducted to explore the relationship of metabolic abnormalities at baseline and at follow-up with risks of DKD. High TG was defined by TG ≥1.70 mmol/L. Low high-density lipoprotein cholesterol (HDL-c) was defined by HDL-c <1.0 mmol/L for men or <1.3 mmol/L for women.

RESULTS

Participants who developed DKD had higher levels of waist circumference and systolic blood pressure, and lower levels of HDL-c at both baseline and follow-up visits. The DKD group also had higher levels of post-load plasma glucose and TG at follow-up. Multivariate logistic regression analysis revealed that both high TG at baseline [odds ratio (OR) = 1.37, p = .012) and high TG at follow-up (OR = 1.71, p < .001) were significantly associated with increased risks of DKD. Patients with high TG levels at both baseline and follow-up had higher risk of DKD compared with constantly normal TG (OR = 1.65, p < .001) after adjustment for covariates.

CONCLUSIONS

In a large population of patients with new-onset type 2 diabetes, a high TG level was an independent risk factor for the development of DKD. Tight TG control might delay the occurrence of DKD.

Prognostic models of diabetic microvascular complications: a systematic review and meta-analysis

BACKGROUND

Many prognostic models of diabetic microvascular complications have been developed, but their performances still varies. Therefore, we conducted a systematic review and meta-analysis to summarise the performances of the existing models.

METHODS

Prognostic models of diabetic microvascular complications were retrieved from PubMed and Scopus up to 31 December 2020. Studies were selected, if they developed or internally/externally validated models of any microvascular complication in type 2 diabetes (T2D).

RESULTS

In total, 71 studies were eligible, of which 32, 30 and 18 studies initially developed prognostic model for diabetic retinopathy (DR), chronic kidney disease (CKD) and end stage renal disease (ESRD) with the number of derived equations of 84, 96 and 51, respectively. Most models were derived-phases, some were internal and external validations. Common predictors were age, sex, HbA1c, diabetic duration, SBP and BMI. Traditional statistical models (i.e. Cox and logit regression) were mostly applied, otherwise machine learning. In cohorts, the discriminative performance in derived-logit was pooled with C statistics of 0.82 (0.73‑0.92) for DR and 0.78 (0.74‑0.83) for CKD. Pooled Cox regression yielded 0.75 (0.74‑0.77), 0.78 (0.74‑0.82) and 0.87 (0.84‑0.89) for DR, CKD and ESRD, respectively. External validation performances were sufficiently pooled with 0.81 (0.78‑0.83), 0.75 (0.67‑0.84) and 0.87 (0.85‑0.88) for DR, CKD and ESRD, respectively.

CONCLUSIONS

Several prognostic models were developed, but less were externally validated. A few studies derived the models by using appropriate methods and were satisfactory reported. More external validations and impact analyses are required before applying these models in clinical practice.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018105287.

Role of Thioredoxin-Interacting Protein in Diabetic Fatty Kidney Induced by Advanced Glycation End-Products

Advanced glycation end-products (AGEs) have been identified as the etiological factors associated with the fatty kidney. Thioredoxin-interacting protein (TXNIP) might be a mediator involved in AGE-induced fatty kidney. This study focused on investigating how TXNIP affected the AGE-mediated renal lipid deposition. In an in vivo experiment, the db/db mice injected with the lentiviral vector encoding shRNA targeting TXNIP were given the AIN-76 basal or the high-AGE diet. TXNIP-targeting siRNA-transfected human renal proximal tubular epithelial (HK-2) cells were exposed to AGE-BSA in a study in vitro. The results showed that the silencing of TXNIP reduced tubular lipid droplets and intracellular cholesterol content, as well as upregulated Insig-1 and downregulated HMGCoAR, LDLr, nSREBP-2, and SCAP in the kidneys of the db/db mice, the high-AGE-diet-fed db/db mice, and AGE-BSA-treated HK-2 cells. Furthermore, AGE-BSA enhanced SCAP-SREBP-2 complex formation while promoting their transportation to the Golgi apparatus. However, these could be inhibited by TXNIP silencing in the HK-2 cells. The above findings indicated that TXNIP knockdown mitigated the accumulation of renal tubular lipids in diabetes through the regulation of SCAP, thereby inhibiting the SCAP-SREBP-2 signaling pathway, resulting in reduced cholesterol uptake and synthesis. Therefore, TXNIP might be a potential therapeutic target to treat a diabetic fatty kidney.

Biomarkers of high salt intake

High salt intake is associated with hypertension, which is a leading modifiable risk factor for cardiovascular disease (CVD) and chronic kidney disease (CKD). International Guidelines recommend a large reduction in the consumption of sodium to reduce blood pressure, organ damage, and mortality. In its early stages, the symptoms of CKD are generally not apparent. CKD proceeds in a "silent" manner, necessitating the need for urinary biomarkers to detect kidney damage at an early stage. Since traditional renal biomarkers, such as serum creatinine, are not sufficiently sensitive, difficulties are associated with detecting kidney damage induced by a high salt intake, particularly in normotensive individuals. Several new biomarkers for renal tubular damage, such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), vanin-1, liver-type fatty acid-binding protein (L-FABP), and monocyte chemotactic protein-1 (MCP-1), have recently been identified. However, few studies have investigated early biomarkers for CKD progression associated with a high salt diet. This chapter provides insights into novel biomarkers for CKD in normo- and hypertensive individuals with a high salt intake. Recent studies using spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) fed a high salt diet identified urinary vanin-1 and NGAL as early biomarkers for renal tubular damage in SHR and WKY, whereas urinary KIM-1 was a useful biomarker for salt-induced renal injury in SHR only. Clinical studies are needed to confirm these findings.

Panel of novel urine biomarkers for incident microalbuminuria in people with type 2 diabetes mellitus

AIM

The need to identify novel biomarkers for early diagnosis and treatment of diabetic nephropathy is widely recognized. However, only a few studies have investigated the association between biomarkers and the onset of albuminuria. In this study, we aimed to investigate a panel of biomarkers suitable for predicting microalbuminuria.

METHODS

Some 346 Japanese people with type 2 diabetes exhibiting normoalbuminuria were studied. The endpoint was defined as the onset of microalbuminuria. Thirty biomarkers were selected from among urinary biomarkers described in previous studies. A panel of biomarkers was selected using least absolute shrinkage and selection operator (LASSO). The prognostic performance of the developed panel was evaluated.

RESULTS

During a mean follow-up of 6.2 years, 45 people progressed to microalbuminuria. A composite panel of six biomarkers (monocyte chemoattractant protein-1, osteopontin, soluble human tumour necrosis factor receptor-1, tenascin C, vascular endothelial growth factor-A and kidney injury molecule-1) was developed using LASSO. Compared with the basal model comprising estimated GFR and urinary albumin-to-creatinine ratio, addition of these six biomarkers significantly increased the overall C index from 0.773 to 0.824 (P = 0.019). Net reclassification improvement and integrated discrimination improvement were estimated to be 0.412 (P = 0.049) and 0.040 (P = 0.040), respectively. Decision curve analysis also showed that the model with the six novel biomarkers had a better prognostic value for predicting the onset of microalbuminuria. The optimism was moderate or negligible according to measures.

CONCLUSIONS

The panel consisting of six novel urinary biomarkers effectively predicted incident microalbuminuria in people with type 2 diabetes.

Plasma kidney injury molecule-1 (p-KIM-1) levels and deterioration of kidney function over 16 years

BACKGROUND

The kidney injury molecule-1 (KIM-1) has previously been associated with kidney function in rodents and humans. Yet its role as a predictive marker for future decline in kidney function has remained less clear.

METHODS

At baseline (1991-1994), fasting plasma KIM-1 (p-KIM-1) was measured in 4739 participants of the population-based Malmö Diet and Cancer Study. Creatinine and cystatin C were used to calculate estimated glomerular filtration rate (eGFR) according to Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Collaboration 2012 creatinine-cystatin C equation at baseline and follow-up examination (2007-2012). Incident CKD was defined as an eGFR <60 mL/min/1.73 m2 at follow-up.

RESULTS

During a mean follow-up time of 16.6 years, high p-KIM-1 levels were associated with a greater decline in eGFR (quartile 1 -1.36 versus quartile 4 -1.54 mL/min/1.73 m2; P < 0.001). In multivariate analyses, the risk for incident CKD at the follow-up examination was higher among participants with baseline p-KIM-1 levels in the highest quartile {odds ratio [OR] 1.45 [95% confidence interval (CI) 1.10-1.92]} compared with those within the lowest quartile. The relative impact of baseline p-KIM-1 on incidence of CKD [OR 1.20 (95% CI 1.08-1.33) per 1 standard deviation (SD) increase in p-KIM-1] was comparable to those of age and systolic blood pressure (SBP) [OR 1.55 (95% CI 1.38-1.74) and OR 1.21 (95% CI 1.09-1.35) per 1 SD increase, respectively]. Adding p-KIM-1 to a conventional risk model resulted in significantly improved C-statistics (P = 0.04) and reclassified 9% of the individuals into the correct risk direction (continuous net reclassification improvement P = 0.02). Furthermore, the risk for hospitalization due to impaired renal function increased with increasing baseline p-KIM-1 [hazard ratio per 1 SD 1.43; (95% CI 1.18-1.74)] during a mean follow-up time of 19.2 years.

CONCLUSION

Our results show that p-KIM-1 predicts the future decline of eGFR and risk of CKD in healthy middle-aged participants. Whether p-KIM-1 can be used to prioritize preventive action that needs to be further investigated.

Biomarkers of Acute and Chronic Kidney Disease

The current unidimensional paradigm of kidney disease detection is incompatible with the complexity and heterogeneity of renal pathology. The diagnosis of kidney disease has largely focused on glomerular filtration, while assessment of kidney tubular health has notably been absent. Following insult, the kidney tubular cells undergo a cascade of cellular responses that result in the production and accumulation of low-molecular-weight proteins in the urine and systemic circulation. Modern advancements in molecular analysis and proteomics have allowed the identification and quantification of these proteins as biomarkers for assessing and characterizing kidney diseases. In this review, we highlight promising biomarkers of kidney tubular health that have strong underpinnings in the pathophysiology of kidney disease. These biomarkers have been applied to various specific clinical settings from the spectrum of acute to chronic kidney diseases, demonstrating the potential to improve patient care.

The association of renal tubular inflammatory and injury markers with uric acid excretion in chronic kidney disease patients

AIM

To investigate the correlation of renal tubular inflammatory and injury markers with renal uric acid excretion in chronic kidney disease (CKD) patients.

METHODS

Seventy-three patients with CKD were enrolled. Fasting blood and morning urine sample were collected for routine laboratory measurements. At the same time, 24 h of urine was collected for urine biochemistry analyses, and 10 ml was extracted from the 24-h urine sample to further detect renal tubular inflammatory and injury markers, including interleukin-18 (IL-18), interleukin 1β (IL-1β), neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). The patients were divided into three tertile groups according to their 24-h urinary uric acid (24-h UUA) levels (UUA1: 24-h UUA ≤ 393.12 mg; UUA2: 393.12 < 24-h UUA ≤ 515.76 mg; UUA3: 24-h UUA > 515.76 mg). The general clinical and biochemical indexes were compared. Multivariable linear regression models were used to test the association of IL-18/Urinary creatinine concentration (IL-18/CR), IL-1β/CR, NGAL/CR and KIM-1/CR with renal uric acid excretion indicators.

RESULTS

All of tested renal tubular inflammation- and injury-related urinary markers were negatively associated with 24-h UUA and UEUA, and the negative correlation still persisted after adjusting for multiple influencing factors including urinary protein and eGFR. Further group analyses showed that these makers were significantly higher in the UUA1 than in the UUA3 group.

CONCLUSIONS

Our findings suggest that markers of urinary interstitial inflammation and injury in CKD patients are significantly correlated with 24-h UUA and Urinary excretion of uric acid (UEUA), and those with high 24-h UUA have lower levels of these markers. Renal uric acid excretion may also reflect the inflammation and injury of renal tubules under certain conditions.

Circulating kidney injury molecule-1 as a biomarker of renal parameters in diabetic kidney disease

AIMS/INTRODUCTION

Urinary kidney injury molecule-1 (KIM-1) has been associated with proximal tubular damage in human and animal studies. Although it has been recognized as a biomarker of acute kidney injury and chronic kidney disease, its significance in the serum remains unclear. Therefore, we examined the relationship of serum and urinary KIM-1 levels with renal parameters in patients with type 2 diabetes.

MATERIALS AND METHODS

Serum and urinary KIM-1 levels, together with urinary liver-type fatty acid-binding protein, were measured in 602 patients with type 2 diabetes and an estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m2 . These were then compared with the urinary albumin-to-creatinine ratio and eGFR.

RESULTS

The serum and urinary KIM-1 levels were significantly different among the three (eGFR ≥60, 45-59, <45 mL/min/1.73 m2 ) groups. These levels were positively associated with the albumin-to-creatinine ratio and negatively associated with eGFR. In a multivariate logistic model, both serum and urinary KIM-1 were associated with an increased albumin-to-creatinine ratio (>30 mg/g Cr), but only the serum KIM-1 was associated with a lower eGFR (<60 mL/min/1.73 m2 ), after adjustment for covariates.

CONCLUSIONS

Renal parameters appear to be strongly associated with serum KIM-1, and not urinary KIM-1, in patients with type 2 diabetes and an eGFR ≥30 mL/min/1.73 m2 .

Urine Markers of Kidney Tubule Cell Injury and Kidney Function Decline in SPRINT Trial Participants with CKD

BACKGROUND AND OBJECTIVES

eGFR and albuminuria primarily reflect glomerular function and injury, whereas tubule cell atrophy and interstitial fibrosis on kidney biopsy are important risk markers for CKD progression. Kidney tubule injury markers have primarily been studied in hospitalized AKI. Here, we examined the association between urinary kidney tubule injury markers at baseline with subsequent loss of kidney function in persons with nondiabetic CKD who participated in the Systolic Blood Pressure Intervention Trial (SPRINT).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 2428 SPRINT participants with CKD (eGFR<60 ml/min per 1.73 m²) at baseline, we measured urine markers of tubule injury (IL-18, kidney injury molecule-1 [KIM-1], neutrophil gelatinase-associated lipocalin [NGAL]), inflammation (monocyte chemoattractant protein-1 [MCP-1]), and repair (human cartilage glycoprotein-40 [YKL-40]). Cox proportional hazards models evaluated associations of these markers with the kidney composite outcome of 50% eGFR decline or ESKD requiring dialysis or kidney transplantation, and linear mixed models evaluated annualized change in eGFR.

RESULTS

Mean participant age was 73±9 (SD) years, 60% were men, 66% were white, and mean baseline eGFR was 46±11 ml/min per 1.73 m². There were 87 kidney composite outcome events during a median follow-up of 3.8 years. Relative to the respective lowest quartiles, the highest quartiles of urinary KIM-1 (hazard ratio, 2.84; 95% confidence interval [95% CI], 1.31 to 6.17), MCP-1 (hazard ratio, 2.43; 95% CI, 1.13 to 5.23), and YKL-40 (hazard ratio, 1.95; 95% CI, 1.08 to 3.51) were associated with higher risk of the kidney composite outcome in fully adjusted models including baseline eGFR and urine albumin. In linear analysis, urinary IL-18 was the only marker associated with eGFR decline (-0.91 ml/min per 1.73 m² per year for highest versus lowest quartile; 95% CI, -1.44 to -0.38), a finding that was stronger in the standard arm of SPRINT.

CONCLUSIONS

Urine markers of tubule cell injury provide information about risk of subsequent loss of kidney function, beyond the eGFR and urine albumin.

Management of Presumed Acute Kidney Injury during Hypertensive Therapy: Stay Calm and Carry on?

BACKGROUND

Recent studies have demonstrated that intensive blood pressure control is associated with improved cardiovascular outcomes. Acute kidney injury (AKI), however, was more common in the intensive treatment group prompting concern in the nephrology community.

SUMMARY

Clinical trials on hypertension control have traditionally defined AKI by changes in serum creatinine. However, serum creatinine has several inherent limitations as a marker of kidney injury, with various factors influencing its production, secretion, and elimination. Urinary biomarkers of kidney injury and repair have the potential to provide insight on the presence and phenotype of kidney injury. In both the Systolic Blood Pressure Intervention Trial and the Action to Control Cardiovascular Risk in Diabetes study, urinary biomarkers have suggested that the increased risk of AKI associated with intensive treatment was due to hemodynamic changes rather than structural kidney injury. As such, clinicians who encounter rises in serum creatinine during intensification of hypertension therapy should "stay calm and carry on." Alternative explanations for serum creatinine elevation should be considered and addressed if appropriate. When the rise in serum creatinine is limited, particularly if albuminuria is stable or improving, intensive blood pressure control should be continued for its potential long-term benefits. Key Messages: Increases in serum creatinine during intensification of blood pressure control may not necessarily reflect kidney injury. Clinicians should evaluate for other contributing factors before stopping therapy. Urinary biomarkers may address limitations of serum creatinine as a marker of kidney injury.

Association of urinary acidification function with the progression of diabetic kidney disease in patients with type 2 diabetes

OBJECTIVE

Although diabetic kidney disease (DKD) has been considered as a glomerulocentric disease in the past few decades, growing evidence demonstrated that tubular damage was indispensable in its pathogenesis and progression. This study was designed to investigate the association of urinary acidification dysfunction with the progression of DKD in type 2 diabetic patients.

METHODS

Here the urinary acidification functions were measured from 80 participants with renal biopsy-proven DKD. The different kinds of renal tubular transportation dysfunction were analyzed, including the dysfunction of bicarbonate reabsorption, titratable acid secretion, and ammonium secretion. In addition, patients were followed up for 17 (interquartile range, 11-32) months to evaluate the effect of urinary acidification dysfunction in the progression of DKD.

RESULTS

The most common urinary acidification dysfunction was the disorder of ammonium secretion, accounting for 53.75%. The more proteinuria excretion and the lower glomerular filtration rate (GFR) were observed in the urinary titratable acid disorder group than the normal group, and the same results were obtained for ammonium secretion disorder. Urine titratable acid was positively correlated with eGFR whereas it was inversely correlated with proteinuria, serum creatinine, and BUN. Moreover, 24 h urine protein, serum creatinine, BUN and cystatin C increased from DKD stage II to stage IV, whereas the eGFR and urine titratable acid decreased in the same way. Furthermore, Kaplan-Meier analysis and Cox regression showed that the disorder of titratable acid was an independent risk factor for DKD progression.

CONCLUSIONS

The dysfunction of urinary titratable acid is a potential biomarker for the severity of proteinuria, eGFR and glomerular lesions in patients with DKD. Moreover, the titratable acid disorder is an independent risk factor of the DKD progression.

Associations of Urine Biomarkers with Kidney Function Decline in HIV-Infected and Uninfected Men

BACKGROUND

HIV-infected (HIV+) persons are at increased risk of chronic kidney disease, but serum creatinine does not detect early losses in kidney function. We hypothesized that urine biomarkers of kidney damage would be associated with subsequent changes in kidney function in a contemporary cohort of HIV+ and HIV-uninfected (HIV-) men.

METHODS

In the Multicenter AIDS Cohort Study, we measured baseline urine concentrations of 5 biomarkers from 2009 to 2011 in 860 HIV+ and 337 HIV- men: albumin, alpha-1-microglobulin (α1m), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), and procollagen type III N-terminal propeptide (PIIINP). We evaluated associations of urine biomarker concentrations with annual changes in estimated glomerular filtration rate (eGFR) using multivariable linear mixed models adjusted for demographics, traditional kidney disease risk factors, HIV-related risk factors, and baseline eGFR.

RESULTS

Over a median follow-up of 4.8 years, the average annual eGFR decline was 1.42 mL/min/1.73 m2/year in HIV+ men and 1.22 mL/min/1.73 m2/year in HIV- men. Among HIV+ men, the highest vs. lowest tertiles of albumin (-1.78 mL/min/1.73 m2/year, 95% CI -3.47 to -0.09) and α1m (-2.43 mL/min/1.73 m2/year, 95% CI -4.14 to -0.73) were each associated with faster annual eGFR declines after multivariable adjustment. Among HIV- men, the highest vs. lowest tertile of α1m (-2.49 mL/min/1.73 m2/year, 95% CI -4.48 to -0.50) was independently associated with faster annual eGFR decline. Urine IL-18, KIM-1, and PIIINP showed no independent associations with eGFR decline, regardless of HIV serostatus.

CONCLUSIONS

Among HIV+ men, higher urine albumin and α1m are associated with subsequent declines in kidney function, independent of eGFR.

Kidney Injury Molecule-1 (KIM-1) in Blood Plasma of Patients with Clear-Cell Carcinoma

The concentration of kidney injury molecule-1 (KIM-1) was measured in blood plasma of 99 patients with clear-cell carcinoma and 14 patients with benign renal tumors using a Human Serum TIM-1/KIM-1/HAVCR Quantikine ELISA kit. The control group consisted of 15 healthy male and 14 healthy female subjects. KIM-1 levels in blood plasma of patients with cancer or benign renal tumors were significantly higher than in the control (p<0.00001 and p<0.01, respectively). In patients with benign tumors, this parameter was significantly lower than in patients with cancer (p<0.0001). KIM-1 level significantly increased with disease stage (p<0.0001), and even in stage I cancer, it was higher than in the control group (p<0.0001) or in patients with benign tumors (p<0.01). The best sensitivity/specificity ratio for stage I renal cancer detection (81 and 83% respectively) was achieved at cut-off level 77 pg/ml, the sensitivity of detection of for stages II-IV being 97%. Plasma level of KIM-1 increased with increasing the size and area of the primary tumor (T). This parameter was higher in patients with metastasis in regional lymph nodes irrespective of their number (N1 or N2) in comparison with patients without regional metastasis (N0). It is also higher in patients with distant metastasis (M+). In patients with grade III-IV cancer, KIM-1 level was 7-fold higher than in patients with grade I-II tumor (p<0.0001). Thus, KIM-1 can be regarded as a highly sensitive marker for early detection of clear-cell carcinoma.

The relationships between markers of tubular injury and intrarenal haemodynamic function in adults with and without type 1 diabetes: Results from the Canadian Study of Longevity in Type 1 Diabetes

OBJECTIVE

Our aim was to define the relationships between plasma biomarkers of kidney injury and intrarenal haemodynamic function (glomerular filtration rate [GFR], effective renal plasma flow [ERPF], renal vascular resistance [RVR]) in adults with type 1 diabetes (T1D).

METHODS

The study sample comprised patients with longstanding T1D (duration ≥50 years), among whom 44 were diabetic kidney disease (DKD) resistors (eGFR >60 mL/min/1.73 m² and <30 mg/d urine albumin excretion) and 22 had DKD, in addition to 73 control participants. GFR_INULIN and ERPF_PAH were measured, RVR was calculated, and afferent (R_A )/efferent (R_E ) areteriolar resistances were derived from Gomez equations. Plasma neutrophil gelatinase-associated lipocalin (NGAL), β2 microglobulin (B2M), osteopontin (OPN) and uromodulin (UMOD) were measured using immunoassay kits from Meso Scale Discovery.

RESULTS

Plasma NGAL, B2M and OPN were higher and UMOD was lower in DKD patients vs DKD resistors and non-diabetic controls. In participants with T1D, plasma NGAL inversely correlated with GFR (r = -0.33; P = 0.006) and ERPF (r = -0.34; P = 0.006), and correlated positively with R_A (r = 0.26; P = 0.03) and RVR (r = 0.31; P = 0.01). In participants without T1D, NGAL and B2M inversely correlated with GFR (NGAL r = -0.18; P = 0.13 and B2M r = -0.49; P < 0.0001) and with ERPF (NGAL r = -0.19; P = 0.1 and B2M r = -0.42; P = 0.0003), and correlated positively with R_A (NGAL r = 0.19; P = 0.10 and B2M r = 0.3; P = 0.01) and with RVR (NGAL r = 0.20; P = 0.09 and B2M r = 0.34; P = 0.003). Differences were significant after adjusting for age, sex, HbA1c, SBP and LDL. There were statistical interactions between T1D status, B2M and intrarenal haemodynamic function (P < 0.05).

CONCLUSIONS

Elevated NGAL relates to intrarenal haemodynamic dysfunction in T1D, whereas elevated NGAL and B2M relate to intrarenal haemodynamic dysfunction in adults without T1D. These data may define a diabetes-specific interplay between tubular injury and intrarenal haemodynamic dysfunction.

Diagnostic Accuracy of Neutrophil Gelatinase-Associated Lipocalin for Predicting Early Diabetic Nephropathy in Patients with Type 1 and Type 2 Diabetes Mellitus: A Systematic Review and Meta-analysis

BACKGROUND

Currently, there is a lack of prediction markers for diabetic nephropathy (DN) in patients with type 1 and type 2 diabetes mellitus (T1DM/T2DM). The aim of this systematic review and meta-analysis was to evaluate the value of a promising biomarker, neutrophil gelatinase-associated lipocalin (NGAL), in both serum and urine for the diagnosis of early DN in T1DM and T2DM patients with different stages of albuminuria.

METHODS

A comprehensive search was performed on PubMed by 2 reviewers until September 2018. Studies in which (a) the degree of DN was determined according to the urinary albumin/creatinine ratio and (b) NGAL was measured in healthy individuals and in diabetes patients with DN were included in the meta-analysis. For each study, a 2 × 2 contingency table was formulated. Sensitivity, specificity, and other estimates of accuracy were calculated using a bivariate random effects model. The hierarchical summary ROC method was used to pool data and to evaluate the area under the curve (AUC). The sources of heterogeneity were explored by subgroup analysis. Publication bias was assessed using the Deeks test.

RESULTS

The meta-analysis enrolled 22 studies involving 683 healthy individuals and 3249 patients with diabetes, of which 488 were T1DM and 2761 were T2DM patients. Overall, pooled sensitivity and specificity among the different settings analyzed ranged from 0.42 (95% CI, 0.22-0.66) to 1.00 (95% CI, 0.99-1.00) and 0.72 (95% CI, 0.62-0.80) to 0.98 (95% CI, 0.50-1.00) in T2DM patients, respectively. For T1DM patients, the corresponding estimates were 0.71 (95% CI, 0.59-0.81) to 0.89 (95% CI, 0.64-0.97) and 0.72 (95% CI, 0.62-0.80) to 0.79 (95% CI, 0.67-0.87). The AUC of NGAL for T2DM patients ranged from 0.69 (95% CI, 0.65-0.73) to 1.00 (95% CI, 0.99-1.00) in the different settings.

CONCLUSION

The results of this meta-analysis suggest that NGAL in both serum and urine can be considered a valuable biomarker for early detection of DN in diabetes patients.

Elevated urinary lipocalin-2, interleukin-6 and monocyte chemoattractant protein-1 levels in children with congenital ureteropelvic junction obstruction

INTRODUCTION

In children with congenital ureteropelvic junction obstruction (UPJO), urinary biomarkers could assist in the diagnosis of renal damage or kidneys at risk for damage. Urinary levels of interleukin-6 (IL6), neutrophil gelatinase-associated lipocalin (LCN2), monocyte chemoattractant protein-1 (MCP1), and transforming growth factor-β1 (TGFB1) proteins have been correlated with renal damage in several contexts. Whether they might be useful non-invasive biomarkers of obstructive nephropathy due to unilateral and bilateral congenital UPJO was tested.

PATIENTS AND METHODS

A cohort study was performed at People's Hospital of Xinjiang Uygur Autonomous Region in China. Bladder urine samples from 17 patients with UPJO were obtained before surgical intervention and from 17 healthy age-matched controls. Levels of IL6, LCN2, MCP1, and TGFB1 were determined by enzyme-linked immunosorbent assay and normalized to urinary creatinine levels.

RESULTS

Levels of urinary LCN2, MCP1, and IL6 were significantly elevated in the urine from individuals with UPJO compared with controls (P = 0.0003, P = 0.0003, and P = 0.0073, respectively). Children with bilateral UPJO (n = 5) showed significantly higher levels of IL6, LCN2, and MCP1 protein in their urine compared with controls or those with unilateral UPJO (n = 12; P = 0.007, P < 0.0001, and P = 0.0002, respectively). Combining LCN2 and MCP1 slightly improved biomarker performance.

DISCUSSION

Urinary biomarkers could be used in obstructed patients to monitor for renal damage and might find particular utility on patients with bilateral UPJO. Monitoring urinary biomarkers and imaging features in untreated patients could provide insights into the natural history of renal damage due to obstruction and will be necessary to test their performance characteristics as biomarkers.

CONCLUSIONS

Urinary levels of LCN2 and MCP1 protein are promising biomarkers monitoring children with UPJO, particularly in those with bilateral disease.

Relation of Serum and Urine Renal Biomarkers to Cardiovascular Risk in Patients with Type 2 Diabetes Mellitus and Recent Acute Coronary Syndromes (From the EXAMINE Trial)

A deeper understanding of the interplay between the renal axis and cardiovascular (CV) disease is needed in type 2 diabetes mellitus (T2DM). We aimed to explore the prognostic value of a comprehensive panel of renal biomarkers in patients with T2DM at high CV risk. We evaluated the prognostic performance of both serum (Cystatin C) and urine renal biomarkers (neutrophil gelatinase-associated lipocalin, kidney injury molecule-1 protein, and indices of urinary protein excretion) in 5,380 patients with T2DM and recent acute coronary syndromes in the EXAMINE trial. Patients requiring dialysis within 14 days were excluded. Single- and multimarker covariate-adjusted Cox proportional hazards models were developed to predict times to events. Primary endpoint was composite nonfatal myocardial infarction, nonfatal stroke, or CV death. Median age was 61 years, 68% were men, and mean baseline estimated glomerular filtration rate (eGFR) was 74 mL/min/1.73 m². During median follow-up of 18 months, 621 (11.5%) experienced the primary endpoint and 326 (6.1%) patients had died. All renal biomarkers were robustly associated with adverse CV events in step-wise fashion, independent of baseline eGFR. However, in the multimarker prediction model, only Cystatin C (per 1 SD) was associated with the primary endpoint (hazard ratio [HR] 1.28 [1.14 to 1.45]; p ≤ 0.001), death (HR 1.51 [1.30 to 1.74]; p ≤ 0.001), and heart failure hospitalization (HR 1.20 [0.96 to 1.49]; p = 0.11). Association between Cystatin C and the primary endpoint was similar in baseline eGFR above and below 60 mL/min/1.73 m² (P_interaction > 0.05). In conclusion, serum and urine renal biomarkers, when tested alone, independently predict long-term adverse CV events in high-risk patients with T2DM. In an integrative panel of renal biomarkers, only serum Cystatin C remained independently associated with subsequent CV risk. Renal biomarkers informing various aspects of kidney function may further our understanding of the complex interplay between diabetic kidney disease and CV disease.

Effect of Intensive Blood Pressure Lowering on Kidney Tubule Injury: Findings From the ACCORD Trial Study Participants

RATIONALE & OBJECTIVE

Random assignment to intensive blood pressure (BP) lowering (systolic BP<120mmHg) compared to a less intensive BP target (systolic BP<140mmHg) in the Action to Control Cardiovascular Risk in Diabetes BP (ACCORD-BP) trial resulted in a more rapid decline in estimated glomerular filtration rate (eGFR). Whether this reflects hemodynamic effects or intrinsic kidney damage is unknown.

STUDY DESIGN

Longitudinal analysis of a subgroup of clinical trial participants.

SETTINGS & PARTICIPANTS

A subgroup of 529 participants in ACCORD-BP.

EXPOSURES

Urine biomarkers of tubular injury (kidney injury molecule 1, interleukin 18 [IL-18]), repair (human cartilage glycoprotein 39 [YKL-40]), and inflammation (monocyte chemoattractant protein 1) at baseline and year 2.

OUTCOMES

Changes in eGFR from baseline to 2 years.

ANALYTICAL APPROACH

We compared changes in biomarker levels and eGFRs across participants treated to an intensive versus less intensive BP goal using analysis of covariance.

RESULTS

Of 529 participants, 260 had been randomly assigned to the intensive and 269 to the standard BP arm. Mean age was 62±6.5 years and eGFR was 90mL/min/1.73m2. Baseline clinical characteristics, eGFRs, urinary albumin-creatinine ratios (ACRs), and urinary biomarker levels were similar across BP treatment groups. Compared to less intensive BP treatment, eGFR was 9.2mL/min/1.73m2 lower in the intensive BP treatment group at year 2. Despite the eGFR reduction, within this treatment group, ACR was 30% lower and 4 urinary biomarker levels were unchanged or lower at year 2. Also within this group, participants with the largest declines in eGFRs had greater reductions in urinary IL-18 and YKL-40 levels. In a subgroup analysis of participants developing incident chronic kidney disease (sustained 30% decline and eGFR<60mL/min/1.73m2; n=77), neither ACR nor 4 biomarker levels increased in the intensive treatment group, whereas the level of 1 biomarker, IL-18, increased in the less intensive treatment group.

LIMITATIONS

Few participants with advanced baseline chronic kidney disease. Comparisons across treatment groups do not represent comparisons of treatment arms created solely through randomization.

CONCLUSIONS

Among a subset of ACCORD-BP trial participants, intensive BP control was associated with reductions in eGFRs, but not with an increase in injury marker levels. These findings support that eGFR decline observed with intensive BP goals in ACCORD participants may predominantly reflect hemodynamic alterations.

Markers of Glomerular and Tubular Damage in the Early Stage of Kidney Disease in Type 2 Diabetic Patients

Diabetic kidney disease develops in half of genetically predisposed patients with type 2 diabetes (T2DM). Early diagnosis of kidney damage and nephroprotective treatment are the ways of preventing the disease progression. Our aim was to evaluate selected laboratory markers of glomerular and tubular damage in T2DM patients with early stages of chronic kidney disease (G1/G2, A1/A2) for their associations with A2 albuminuria and early decline in the estimated glomerular filtration rate (eGFR). Among 80 T2DM patients with median eGFR of 92.4 ml/min/1.73 m² and median urinary albumin to creatinine ratio (uACR) of 4.69 mg/g, 19 had uACR > 30 mg/g (A2). Higher serum cystatin C, serum and urine neutrophil gelatinase associated lipocalin (NGAL), urine kidney injury molecule 1 (KIM-1), detectable urine transferrin and IgG, and lower serum uromodulin significantly predicted A2 albuminuria, urine KIM-1/creatinine ratio, and IgG being the best predictors. Albuminuria, urine NGAL/creatinine, and IgG correlated with diabetes duration. Albuminuria, urine NGAL, transferrin, IgG, and uromodulin correlated with diabetes control. In a subgroup of 29 patients, retrospective data were available on changes in eGFR and uACR over one year. Decline in eGFR was observed in 17 patients and increase in uACR in 10 patients. Serum and urine NGAL correlated with eGFR changes. Higher urine NGAL, KIM-1/creatinine ratio, and detectable IgG were significantly associated with the increase in uACR. Widely available markers, serum cystatin C, urine IgG, transferrin, and NGAL, may help in early assessment of kidney disease in T2DM patients; however, large prospective studies are needed to confirm the conclusion.

Identification of Novel Urinary Biomarkers for Predicting Renal Prognosis in Patients With Type 2 Diabetes by Glycan Profiling in a Multicenter Prospective Cohort Study: U-CARE Study 1

OBJECTIVE

Because quantifying glycans with complex structures is technically challenging, little is known about the association of glycosylation profiles with the renal prognosis in diabetic kidney disease (DKD).

RESEARCH DESIGN AND METHODS

In 675 patients with type 2 diabetes, we assessed the baseline urinary glycan signals binding to 45 lectins with different specificities. The end point was a decrease of estimated glomerular filtration rate (eGFR) by ≥30% from baseline or dialysis for end-stage renal disease.

RESULTS

During a median follow-up of 4.0 years, 63 patients reached the end point. Cox proportional hazards analysis revealed that urinary levels of glycans binding to six lectins were significantly associated with the outcome after adjustment for known indicators of DKD, although these urinary glycans, except that for DBA, were highly correlated with baseline albuminuria and eGFR. Hazard ratios for these lectins were (+1 SD for the glycan index) as follows: SNA (recognizing glycan Siaα2-6Gal/GalNAc), 1.42 (95% CI 1.14-1.76); RCA120 (Galβ4GlcNAc), 1.28 (1.01-1.64); DBA (GalNAcα3GalNAc), 0.80 (0.64-0.997); ABA (Galβ3GalNAc), 1.29 (1.02-1.64); Jacalin (Galβ3GalNAc), 1.30 (1.02-1.67); and ACA (Galβ3GalNAc), 1.32 (1.04-1.67). Adding these glycan indexes to a model containing known indicators of progression improved prediction of the outcome (net reclassification improvement increased by 0.51 [0.22-0.80], relative integrated discrimination improvement increased by 0.18 [0.01-0.35], and the Akaike information criterion decreased from 296 to 287).

CONCLUSIONS

The urinary glycan profile identified in this study may be useful for predicting renal prognosis in patients with type 2 diabetes. Additional investigation of glycosylation changes and urinary glycan excretion in DKD is needed.

Urinary Tubular Injury Biomarkers Are Associated With ESRD and Death in the REGARDS Study

Introduction

Urinary neutrophil gelatinase-associated lipocalin (uNGAL) and urinary kidney injury molecule-1 (uKIM-1) are established markers of subclinical acute kidney injury. In persons with reduced estimated glomerular filtration rate (eGFR) and albuminuria who are at high risk for end-stage renal disease (ESRD) and death, the associations of these urinary markers with incident ESRD or death is an area of active investigation.

Methods

Among 1472 black and white participants from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study with eGFR ≤60 ml/min per 1.73 m² (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] cystatin, 2012) and albumin-to-creatinine ratio (ACR) ≥30 mg/g, we evaluated the associations of baseline uNGAL and uKIM-1 with progression to ESRD and all-cause death. Cox models were sequentially adjusted for urinary creatinine, traditional risk factors, C-reactive protein, ACR, and eGFR.

Results

There were 257 ESRD events and 819 deaths over a median follow-up of 5.7 and 6.5 years, respectively. In demographic adjusted models, higher levels of uNGAL were associated with increased risk of ESRD and death, but these associations were attenuated in fully adjusted models including baseline eGFR for both ESRD (hazard ratio [HR] = 1.06 per doubling, 95% confidence interval [CI] 0.98-1.14) and death (HR = 1.04, 95% CI = 1.00-1.08). Higher levels of uKIM-1 were associated with increased risk of ESRD and death in demographic-adjusted models, and although attenuated in fully adjusted models, remained statistically significant for both ESRD (HR = 1.24 per doubling, 95% CI = 1.08-1.42) and death (HR = 1.10, 95% CI =1.03-1.19).

Conclusion

In this cohort of high-risk patients with baseline eGFR ≤60 ml/min per 1.73 m² and albuminuria, renal tubular injury is associated with higher mortality and progression to ESRD. Further studies are necessary to investigate the mechanism underlying this increased risk.

Biomarkers of diabetic kidney disease

Diabetic kidney disease (DKD) remains one of the leading causes of reduced lifespan in diabetes. The quest for both prognostic and surrogate endpoint biomarkers for advanced DKD and end-stage renal disease has received major investment and interest in recent years. However, at present no novel biomarkers are in routine use in the clinic or in trials. This review focuses on the current status of prognostic biomarkers. First, we emphasise that albuminuria and eGFR, with other routine clinical data, show at least modest prediction of future renal status if properly used. Indeed, a major limitation of many current biomarker studies is that they do not properly evaluate the marginal increase in prediction on top of these routinely available clinical data. Second, we emphasise that many of the candidate biomarkers for which there are numerous sporadic reports in the literature are tightly correlated with each other. Despite this, few studies have attempted to evaluate a wide range of biomarkers simultaneously to define the most useful among these correlated biomarkers. We also review the potential of high-dimensional panels of lipids, metabolites and proteins to advance the field, and point to some of the analytical and post-analytical challenges of taking initial studies using these and candidate approaches through to actual clinical biomarker use.

Urinary biomarkers reporting weakness and validation failure in Type 2 diabetic nephropathy: systematic review

For better identification of novel diagnostic urinary biomarker in Type 2 diabetic nephropathy (T2DN), methodological and reporting quality is as important as validity of biomarkers. The aim of this systematic review is to find out the best-reported diagnostic urinary biomarkers study in T2DN based on STARD criteria. We also analyzed the validity of urinary markers in the selected articles those followed STARD criteria. The diagnostic accuracy of urinary biomarkers on T2DN is not conclusive because of the poor reporting quality and differences in adjustment for conventional risk factors. For a proper validation of urinary biomarkers on T2DN, in future large well-designed longitudinal studies, with specific prediction analysis and validation of the biomarkers by adjusting with possible conventional risk factors.

Kidney Biomarkers and Decline in eGFR in Patients with Type 2 Diabetes

BACKGROUND AND OBJECTIVES

Biomarkers may improve identification of individuals at risk of eGFR decline who may benefit from intervention or dialysis planning. However, available biomarkers remain incompletely validated for risk stratification and prediction modeling.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined serum cystatin C, urinary kidney injury molecule-1 (uKIM-1), and urinary neutrophil gelatinase-associated lipocalin (UNGAL) in 5367 individuals with type 2 diabetes mellitus and recent acute coronary syndromes enrolled in the Examination of Cardiovascular Outcomes with Alogliptin versus Standard of Care (EXAMINE) trial. Baseline concentrations and 6-month changes in biomarkers were also evaluated. Cox proportional regression was used to assess associations with a 50% decrease in eGFR, stage 5 CKD (eGFR<15 ml/min per 1.73 m2), or dialysis.

RESULTS

eGFR decline occurred in 98 patients (1.8%) over a median of 1.5 years. All biomarkers individually were associated with higher risk of eGFR decline (P<0.001). However, when adjusting for baseline eGFR, proteinuria, and clinical factors, only baseline cystatin C (adjusted hazard ratio per 1 SD change, 1.66; 95% confidence interval, 1.41 to 1.96; P<0.001) and 6-month change in urinary neutrophil gelatinase-associated lipocalin (adjusted hazard ratio per 1 SD change, 1.07; 95% confidence interval, 1.02 to 1.12; P=0.004) independently associated with CKD progression. A base model for predicting kidney function decline with nine standard risk factors had strong discriminative ability (C-statistic 0.93). The addition of baseline cystatin C improved discrimination (C-statistic 0.94), but it failed to reclassify risk categories of individuals with and without eGFR decline.

CONCLUSIONS

The addition of cystatin C or biomarkers of tubular injury did not meaningfully improve the prediction of eGFR decline beyond common clinical factors and routine laboratory data in a large cohort of patients with type 2 diabetes and recent acute coronary syndrome.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_01_16_CJASNPodcast_18_3_G.mp3.

The Promise of Systems Biology for Diabetic Kidney Disease

Diabetic kidney disease (DKD) has a complex and prolonged pathogenesis involving many cell types in the kidney as well as extrarenal factors. It is clinically silent for many years after the onset of diabetes and usually progresses over decades. Given this complexity, a comprehensive and unbiased molecular approach is best suited to help identify the most critical mechanisms responsible for progression of DKD and those most suited for targeted intervention. Systems biological investigations provide such an approach since they examine the entire network of molecular changes that occur in a disease process in a comprehensive way instead of focusing on a single abnormal molecule or pathway. Systems biological studies can also start with analysis of the disease in humans, not in animal or cell culture models that often poorly reproduce the changes in human DKD. Indeed, in the last decade, systems biological approaches have led to the identification of critical molecular abnormalities in DKD and have directly led to development of new biomarkers and potential treatments for DKD.

Biomarkers for predicting outcomes in chronic kidney disease

PURPOSE OF REVIEW

Current biomarkers for chronic kidney disease (CKD) are limited by lack of sensitivity and inability to prognosticate CKD progression. Significant recent research has better characterized novel biomarker candidates that are associated with CKD progression and cardiovascular mortality in CKD. This review discusses the most significant advances within the past year.

RECENT FINDINGS

We discuss biomarkers for outcomes in CKD under two categories: emerging (defined as having been validated in an independent cohort), which include serum cystatin C, serum β-trace protein, β2-microglobulin, soluble urokinase-type plasminogen activator receptor, soluble tumor necrosis factor receptors 1/2, urinary monocyte chemotactic protein-1, neutrophil gelatin-associated lipocalin, kidney injury molecule-1, and fibroblast growth factor-23; and novel (which have shown associations in smaller observational studies but have not been validated yet), which include indoxyl sulfate, p-cresyl sulfate, trimethylamine-N-oxide, IL-18, Klotho, markers of endothelial dysfunction, vimentin, and procollagen type III N-terminal propeptide. Further, we also discuss future directions for biomarker research including unbiased -omics approaches.

SUMMARY

There are a number of promising biomarkers that can better prognosticate outcomes in and progression of CKD. Further research is warranted to examine whether these biomarkers validate independently as well, and if their incorporation improves clinical practice or trial enrollment.

Subclinical First Trimester Renal Abnormalities Are Associated With Preeclampsia in Normoalbuminuric Women With Type 1 Diabetes

OBJECTIVE

This study was conducted to determine the utility of tubular (urinary/plasma neutrophil gelatinase-associated lipocalin [NGAL] and urinary kidney injury molecule 1 [KIM-1]) and glomerular (estimated glomerular filtration rate [eGFR]) biomarkers in predicting preeclampsia (PE) in pregnant women with type 1 diabetes mellitus (T1DM) who were free of microalbuminuria and hypertension at the first trimester.

RESEARCH DESIGN AND METHODS

This was a prospective study of T1DM pregnancy. Maternal urinary and plasma NGAL, urinary KIM-1 (ELISA of frozen samples), and eGFR (Chronic Kidney Disease Epidemiology Collaboration equation) were determined at three study visits (V1: 12.4 ± 1.8; V2: 21.7 ± 1.4; V3: 31.4 ± 1.5 weeks' gestation [mean ± SD]) in 23 women with T1DM with subsequent PE (DM+PE+), 24 who remained normotensive (DM+PE-), and, for reference, in 19 normotensive pregnant women without diabetes (DM-). The groups with diabetes were matched for age, diabetes duration, and parity. All subjects were normotensive and free of microalbuminuria or albuminuria at V1. All study visits preceded the onset of PE.

RESULTS

Urinary creatinine-corrected NGAL (uNGALcc, ng/mg) was significantly elevated at V1 in DM+PE+ vs. DM+PE- women (P = 0.01); this remained significant after exclusion of leukocyte-positive samples (5 DM+PE+ and 2 DM+PE-) (P = 0.02). Accounting for BMI, HbA_1c, and total daily insulin dose, a doubling of uNGALcc at V1 conferred a sevenfold increase in risk for PE (P = 0.026). In contrast, neither plasma NGAL nor urinary KIM-1 predicted PE. Also at V1, eGFR was elevated in DM+PE+ vs. DM+PE- (P = 0.04).

CONCLUSIONS

Early tubular and glomerular dysfunction may predict PE in first trimester women with T1DM, even if free of microalbuminuria. These data suggest that subclinical renal tubular and glomerular injury, if present early in pregnancy, may predispose women with T1DM to PE.

Early term effect of ureterorenoscopy (URS) on the Kidney: research measuring NGAL, KIM-1, FABP and CYS C levels in urine

Aim:

URS is a very commonly used procedure for treatment of ureter stones. Increased hydrostatic pressure in the collecting system linked to fluids used during the procedure may cause harmful effects on the kidney. The aim of this study is to determine whether the URS procedure has a negative effect on the kidney by investigating NGAL, KIM-1, FABP and Cys C levels in urine.

Material and Methods:

This study included 30 patients undergoing ureterorenoscopy (URS) for ureter stones. Urine samples were collected 5 times; before the URS procedure (control) and at 1, 3, 5 and 12 hours following the procedure. NGAL, KIM-1, FBAP and Cys C levels were measured in urine and compared with the control values.

Results:

The NGAL levels in urine before the procedure and at 1, 3, 5 and 12 hours after the procedure were 34.59±35.34; 62.72±142.32; 47.15±104.48; 45.23±163.16 and 44.99±60.79ng/mL, respectively (p=0.001). Similarly, the urinary KIM-1, FABP and Cys C levels were found to increase compared to control values; however this increase did not reach statistical significance (p >0.05).

Conclusions:

After the URS procedure, there were important changes in NGAL, FABP, KIM-1 and Cys C levels. These changes reached statistical significance for NGAL, but did not reach significance for the other parameters. In conclusion, the URS procedure significantly affects the kidney; however, this effect disappears over time.